1. Field of the Invention
The present invention relates to a display device and a method of manufacturing the same, and more particularly, to a display device with a parallax barrier layer, and a method of manufacturing the same.
2. Description of Related Art
In recent years, liquid crystal display devices (LCDs) for displaying an image that varies depending on viewing angles are applied as 3D-LCDs and dual-screen LCDs. A 3D-LCD displays a 3D image using a parallax generated by allowing the viewer's right and left eyes to perceive images seen from different points. Thus, the 3D-LCD is also called a three-dimensional liquid crystal display device (e.g., Japanese Unexamined Patent Application Publication No. 11-95167). Meanwhile, a dual-screen LCD provides two different types of images simultaneously to a plurality of viewers located at different viewing positions. Thus, the dual-screen LCD is also called a dual-view liquid crystal display device (e.g., “Regarding “dual-view LCD” and “triple-view LCD”” written by Tomoo Takatani, Sharp Technical Journal, No. 96, November 2007, pp. 21-23). A triple-screen LCD provides three different types of images simultaneously to a plurality of viewers located at different viewing positions. Thus, the triple-screen LCD is also called a triple-view liquid crystal display device.
In these liquid crystal display devices, angles at which an image is viewed are generally separated by a stripe-shaped parallax barrier pattern formed in a display area. As a method of forming such a parallax barrier pattern, Japanese Unexamined Patent Application Publication Nos. 11-95167 and 2008-8934 (see FIG. 1 of the publication) disclose a method in which, after an LCD is completed, a glass substrate with a parallax barrier having a parallax barrier pattern formed therein is bonded to the completed LCD.
In this method, however, a bonding failure inevitably occurs at a constant rate during the bonding process. Accordingly, it is expected that the LCD, which is a component of high value, becomes defective, resulting in increase in cost. Additionally, it is necessary to accurately align and bond the glass substrate with the parallax barrier for each LCD, resulting in deterioration in productivity.
As a related art modified in view of the above-mentioned problems, there is proposed a method of directly forming a parallax barrier pattern on a substrate constituting an LCD which is disposed on a visible-side or backlight side.
For example, International Patent Publication No. WO 2004/011987 discloses a method of forming a parallax barrier pattern on the outer surface of a panel of a color filter substrate placed on the visible-side. Japanese Unexamined Patent Application Publication No. 2005-258016 discloses a method of forming a parallax barrier pattern on the inner surface of a panel of a color filter substrate placed on the backlight side. Japanese Unexamined Patent Application Publication No. 2008-8934 discloses a method of forming a parallax barrier layer on a substrate of a display device which is a liquid crystal cell serving as a display element body (see FIGS. 9 to 13 of the publication). Specifically, a display device is prepared in advance, and a first parallax barrier layer, a first adhesion layer, and a first glass substrate are stacked on an opposing substrate constituting the display device.
Furthermore, a second parallax barrier layer, a second adhesion layer, and a second glass substrate are stacked on the first glass substrate.
In the method disclosed in International Patent Publication No. WO 2004/011987, however, when the parallax barrier pattern disposed outside the panel is formed using a metallic film such as chromium oxide, which is an ordinary light-shielding film, and then a black matrix pattern disposed inside the panel is formed using the same metallic film, the parallax barrier pattern is also etched during the process for etching the black matrix. Accordingly, it is necessary to separately carry out resist pattern forming and removing processes to protect the parallax barrier pattern. This causes a problem of an increase in the number of steps.
On the other hand, when one of the parallax barrier pattern and the black matrix pattern is formed using a black resin, instead of forming the both patterns using the same metallic film, the use of the black resin makes it difficult to achieve thinning. This causes a problem that it is difficult to apply such a method to a high-definition LCD. Thus, the method disclosed in International Patent Publication No. WO 2004/011987 has problems involving the light-shielding film.
Meanwhile, in the LCD that displays different images depending on viewing angles, it is necessary to set a predetermined distance between one of a liquid crystal layer and a color filter layer, which is located closer to a parallax barrier layer, and the parallax barrier layer to in order to separate a display image into a left side image and a right side image. This distance varies depending on a pitch of LCD pixels and an angle of luminance peaks of the left side image and the right side image. In the case of the dual-screen LCD, the distance is equal to or smaller than about 0.5 mm, e.g., about 0.1 mm or 0.3 mm.
However, when the parallax barrier layer is disposed outside the panel as disclosed in International Patent Publication No. WO 2004/011987, it is necessary to set the thickness of the substrate to about 0.5 mm or smaller. Thus, the substrate strength is insufficient, which makes difficult to manufacture the LCD. In view of this, in the method disclosed in Japanese Unexamined Patent Application Publication No. 2005-258016, after the parallax barrier pattern is formed on the inner surface of the panel of the color filter substrate, a thick resin layer having a thickness of about 0.1 mm or 0.3 mm is formed so as to adjust the distance between one of the liquid crystal layer and the color filter layer and the parallax barrier layer.
When the thick resin layer having a thickness of about 0.1 mm or 0.3 mm is formed on the color filter substrate, however, a warp occurs in the glass substrate due to a stress of the thick resin layer. This may make it difficult to continuously perform the subsequent manufacturing steps. Besides, a crack or a wrinkle may occur in the thick resin layer due to its shrinkage, resulting in deterioration of the display quality. Thus, the method disclosed in Japanese Unexamined Patent Application Publication No. 2005-258016 has problems involving the thick resin layer.
Additionally, in the method disclosed in Japanese Unexamined Patent Application Publication No. 2008-8934, the parallax barrier layer, the adhesion layer, and the glass substrate are formed after the display device is prepared. Accordingly, the productivity thereof is not high. Besides, since two sets of the parallax barrier layer, the adhesion layer, and the glass substrate are stacked, the productivity thereof is not high.